1. Field of the Invention
The present invention relates to an optical device in which the optical axis of a light source unit including a light source can be adjusted so as to be appropriately directed and the light source unit can be fixed to a holding body.
2. Description of the Related Art
A light-emitting device in which a light source unit including a light source is held is used in various information processing apparatuses. In such a light-emitting device, the light source unit has to be adjusted in tilt attitude and fixed such that the optical axis of light emitted from the light source unit is appropriately directed.
Japanese Unexamined Patent Application Publication No. 2008-10492 discloses a light-emitting device mounted on an optical head apparatus. In the light-emitting device, the outer peripheral surface of an element-side holder which supports a semiconductor laser is a convexly curved surface having an arcuate cross-sectional shape, a positioning region formed at an opening of a fixed-side holder is a concavely curved surface having an arcuate cross-sectional shape, and the curvature radii of the convexly curved surface and the concavely curved surface are the same.
The convexly curved surface is brought into contact with the concavely curved surface, and the convexly curved surface and the concavely curved surface are slid relative to each other to change the tilt angle of the element-side holder, thereby adjusting the optical axis of the semiconductor laser. After the adjustment, the element-side holder is fixed to the fixed-side holder by means of an anaerobic adhesive.
In the light-emitting device disclosed in Japanese Unexamined Patent Application Publication No. 2008-10492, the convexly curved surface in the element-side holder and the concavely curved surface in the fixed-side holder are formed so as to have the same curvature radius and are brought into contact with each other entirely around the optical axis. However, since there is a limit on processing accuracy of the convexly curved surface and the concavely curved surface, it is impossible to accurately cause the convexly curved surface and the concavely curved surface to closely contact each other entirely around the optical axis, and the gap in the fitted portion between the element-side holder and the fixed-side holder is likely to vary depending on a location around the optical axis. Therefore, the adhesion stress by the adhesive interposed between both holders is different depending on a location, and an angle shift of the optical axis is likely to occur when the adhesive is cured after the optical axis is adjusted.
Further, in the structure in which the element-side holder and the fixed-side holder are fixed to each other by means of the adhesive, the adhesive is likely to alter due to temperature change, and thus the fixing stress by the adhesive changes during a long period of use, and problems such as change in the angle of the optical axis of the semiconductor laser are likely to arise.